1. Field of the Invention
The present invention relates to disk drives for computers. More particularly, the present invention relates to apparatus for mechanically latching or "parking" the actuator.
2. The Prior Art
Most disk drives are equipped with some type of arrangement which provides for securing or "parking" the head actuators so that the heads may be held immobilized over a landing zone on a disk at times when the drive is not in use, such as during transportation of the disk drive or the computer in which it is installed. These mechanical latching devices typically comprise either magnetic or mechanical, or a combination of magnetic and mechanical latching means.
Historically, disk drives started as very large immovable devices, weighing over 2000 pounds, and having disk diameters ranging from 2 to 4 feet. Disk sizes have quickly evolved to 14 inches, 5.25 inches, 3.5, inches, 2.5 inches and smaller. As development continues, disk drives are continually shrinking in size to accommodate new applications.
As disk diameters, and hence the drives which contain them become smaller, different issues arise in the design of actuator "parking" mechanisms. As continuing evolution shrinks disk diameters below two inches, mechanical shock becomes an increasingly larger concern in the design of head parking mechanisms. Larger disk drives (i.e., 5.25 inch and 3.5 inch) are generally mounted into computer systems housed in larger cases, usually residing on desk tops, or in even larger "tower" cases which are placed on the floor. In these environments, design of actuator latches for larger disk drives, even the 5.25 inch and 3.5 inch drives, are relatively free from constraints relating to mechanical shocks because the likely-to-be-encountered mechanical shock forces are small compared to the force with which a latch can hold the actuator arm. In addition, because such devices are powered from power supplies connected to electrical utility distribution systems, power consumption is not an issue and can be continuously supplied to a disk drive latching mechanism when desired. The absence of power and space constraints gives the mechanical designer a wide range of options when designing a latching mechanism.
The present concern over mechanical shock as an issue in the design of latching mechanisms results from the development of the small disk drives which are designed to reside in small "laptop" and "notebook" computers and the problems which are presented to designers because of size and other requirements. Such applications present an environment in which bumping and jostling is much more likely. A lap-top computer system weighs from about 5 to 15 pounds. This lower weight increases the likely-to-be-encountered mechanical shock forces which have to be taken into consideration. Such forces are significantly larger than those likely to be encountered in larger disk drives in comparison to the force that an actuator is capable of generating. This means that the ideal latching mechanism has to provide enough latching force to keep the actuator in the desired landing zone position during parking. However, due to the smaller size of the drives, this requirement competes with the requirement that the force necessary to free the actuator from its parked position be reasonably provideable in the small disk drive.
In addition, the applications for which the smaller disk drive units are being considered are largely notebook, lap-top, and palm-top computer applications. Since these smaller computers are designed to be portable and are thus powered for the most part by batteries, power-management considerations require that the disk drives be operable with a minimum amount of power. Furthermore, most such applications require extremely low standby-power requirements for the disk drives when they are not being written to or read from. This power-management requirement restricts latching designs to static embodiments which do not continuously consume power.
Finally, as disk drive sizes continue to shrink, the amount of data area available on the disk decreases. It is thus desirable to maximize the free movement of the actuator to maximize the data area without having to sacrifice movement, and hence useable disk data area, to accommodate the latching mechanism.
These considerations present a significant challenge to the disk drive designer. There is a need for providing a reliable actuator latching mechanism which is adaptable to the several design requirements of small disk drives.